When you hear creationists argue their cause, sooner or later they reach into their standard litany of debunked arguments. One of their favorites (since it sounds convincing to their largely math-illiterate followers) is to point to the complexity of a molecular system or the cell or any other part of nature and “how could such a complicated system arise BY CHANCE?” The bigger implication is that they cannot fathom humans and their religious worldview being produced by anything other than a supernatural creator, so chance (as they misunderstand the concept) cannot produce it. The same argument underlies much of what the “intelligent design” creationists claim as well.
There are many versions of this argument, all of which are equally fallacious. When I debated Duane Gish at Purdue University in 1983, he was using his favorite line of his whole spiel, stolen from the maverick astronomer Fred Hoyle (legendary for being wrong on nearly every thing he argued, including Big Bang cosmology and his attacks on Archaeopteryx and evolution). In Gish’s version, he argues that the probability of random evolution assembling the complex system of life was as likely as a tornado in a junkyard assembling a Boeing 707 (which shows how ancient this punchline was).
As in the case of all creationist arguments, this one is completely fallacious on several different levels:
1. Evolution is not “random chance” like a lottery or throwing the dice. The variation on which natural selection works (mutations, recombination, etc.) is randomly produced, but natural selection is not random. Natural selection is a process that weeds out unfavorable variations, and greatly improves the likelihood of events. Anti-evolutionists for years have used various versions of this fallacious analogy: “what is the probability that a monkey (or chimpanzee) with a typewriter randomly pounding on the keys could produce the works of Shakespeare?” A better analogy is a monkey with a word processor, whose program (like your spell checker) automatically deletes or fixes mistakes, so that even by typing random keys, the monkey will eventually assemble a recognizable string of words. Richard Dawkins (in The Blind Watchmaker, 1986, and Climbing Mount Improbable, 1996) has provided many interesting examples and computer models that show just how easily this can be done. This is the fundamental misunderstanding: evolution is not just “random chance” but a strong non-random force capable of changing genomes and acting upon material provided by chance.
2. Many of the standard examples that creationists trot out seem staggeringly difficult to produce as they present it, but in fact there are numerous small intermediate steps that show it’s not so hard as they imagine. As I discuss in Chapter 6 of my evolution book, since the days of the Miller-Urey experiment in 1953, most of the chemical steps needed to assemble the simplest forms of life (RNA in a lipid bilayer membrane) have all been produced by biochemists in the laboratory using relatively simple chemical reactions. To produce long-chain biochemicals, there are a number of “templates” (clays, zeolites, pyrite, etc.) that assemble simple organic chemicals into long-chain polymers by lining them up all close together, and then their chemical linkages form. (I use the analogy of a mosh pit—everyone packed shoulder to shoulder tightly in the same direction, then their earrings and piercings get hooked together). As Lynn Margulis and others have shown, the eukaryotic cell can be most easily produced by endosymbiosis, where symbiotic prokaryotes like cyanobacteria and purple non-sulfur bacteria have changed to organelles like chloroplasts and mitochondria. With all these intermediate steps that have been discovered in the past 60 years, the origin of life from simple chemicals is no longer as improbable as the creationists like to claim.
3. As anyone who really understands probability knows, you can’t make a probability argument after the fact. If you do so, then any complex sequence of events is extremely improbable, even though they actually occur. A good analogy is the one I used in the Gish debate. I asked the audience of several hundred to estimate the probability after the fact that all of the events that had happened in their lives would actually happen, and the probability that among all those unlikely events, they would all end up in this room at this particular moment. Naturally, the improbability of this event is enormous. I pointed out to the audience that by Gish’s probability arguments, they could not exist! For someone to make a probability argument of this sort, it has to be made ahead of time, because life is full of events that (looked at after the fact) are extremely improbable—yet happened nonetheless.
So the next time you get into an argument with a creationist, don’t let them baffle you with garbage about “random evolution” or “the probabilities say it is impossible”.